5 May 2009 Fiber optic cryogenic liquid level detection system for space applications
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Liquid hydrogen and oxygen are widely used as fuels in space vehicles. Because both are highly dangerous materials prone to explosion, detection of the liquid level in fuel tank becomes a critical element for the safety and efficiency in space operations. Two liquid level sensing techniques are presented in this paper. The first technique is based on optical fiber long period gratings. In this technique, the full length of a specially fabricated fiber is the body of the probe becomes the length of the sensing fiber that is submerged in the liquid can be detected by the interrogation system. The second system uses optical fibers to guide light to and from an array of point probes. These probes are specially fabricated, miniature optical components which reflects a substantial amount of light back into the lead fiber when the probe is gas but almost no light when it is in liquid. A detailed theoretical study by computer simulation was carried out on these two techniques in order to determine which technique was more suitable for experimental investigation. The study revealed that although the first technique may provide more potential benefits in terms of weight and easy installation; a number of technical challenges make it not suitable for a short term solution. The second, probe array based technique, on the other hand, is more mature technically. The rest of the research program was therefore focused on the experimental investigation of the probe array detection technique and the test results are presented in this paper.
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Alex A. Kazemi, Alex A. Kazemi, Chengning Yang, Chengning Yang, Shiping Chen, Shiping Chen, "Fiber optic cryogenic liquid level detection system for space applications", Proc. SPIE 7314, Photonics in the Transportation Industry: Auto to Aerospace II, 73140A (5 May 2009); doi: 10.1117/12.821374; https://doi.org/10.1117/12.821374


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